1. Field of the invention The present invention relates to a communication terminal device and a billing device in a packet communication system.
2. Description of the Related Art
Presently, it is customary for communications carriers which provide Internet connection services using portable telephone sets to charge users based on the number of packets of data that are transmitted and received. Each packet includes a header containing control information representative of a source, a destination, and a sequence of packets, etc. If the size of a packet, i.e., the amount of transmission data (hereinafter referred to as “packet unit”) included in a packet is reduced, then the data transmitted and received per packet is relatively reduced, making the transmission and reception of data inefficient.
Conversely, if the size of a packet unit is increased, then even when a small amount of data is transmitted and received, the user is charged with a rate for the transmitted and received data based on the large packet unit.